Apparatus for determining the percentage of a fluid in a mixture of fluids

ABSTRACT

Disclosed is a method and apparatus for measuring the percentages of oil and water present in an oil/water mixture. By measuring the energy absorption properties of the oil/water mixture, the percentages of oil and water present in the oil/water mixture can be determined regardless of whether the oil or the water is in the continuous phase and regardless of what the relative proportions of water and oil are. Measuring the energy absorption properties of the oil/water mixture yields a current output which can be plotted on one of two distinct, empirically or theoretically derived data curves. One of the data curves represents oil being in the continuous phase and the other data curve represents water being in the continuous phase. A comparator is used to determine whether the oil or the water is in the continuous phase to thereby select the proper data curve on which the energy adsorption is plotted. Each of the curves has the energy absorption properties of the media plotted against the percentage of water and plotting the amount of energy absorbed on the proper curve yields the percentage of water present.

This is a division of pending U.S. application Ser. No. 07/311,610 filedFeb. 15, 1989.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and a method fordetermining the percentage of a fluid present in a mixture of fluids.Specifically, the present invention relates to an apparatus and a methodfor determining the percentage of oil or water in an oil/water mixtureflowing through a predetermined region of a conduit.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a counterpart application of the Britishapplication of Joram Agar, Ser. No. 8803142, filed Feb. 15, 1988,entitled Method and Apparatus for Determining the Percentage of a Fluidin a Mixture of Fluids.

BACKGROUND OF THE INVENTION

The accuracy of net oil measurement is extremely important to buyers andsellers of oil. If the oil contains water, the buyer does not want topay for the oil on the basis of the gross amount of liquid shipped tohim. Rather, he wants to pay only for the net amount of oil present inthe total volume delivered. Net oil measurement is also required in oilfields for royalty payments and in enhanced oil recovery fields forpumping rate control.

There are in the art a number of instruments which have been used tomeasure water content in an oil/water mixture. Most of such instrumentsutilize the dielectric properties of the fluids, e.g., the differencebetween the dielectric constant of water and the dielectric constant ofoil. As such, the main problem with such devices is their inability tooperate with respect to mixtures where the water constituent of themixture is in the continuous phase rather than the oil phase. Bydefinition, the dielectric constant is the ratio of the capacitance of acapacitor field with a given dielectric to that of the same capacitorhaving only a vacuum as the dielectric. Therefore, in using the devicesfor oil/water measurement, when water is the continuous phase, theinstrument will show a maximum value because the electric path betweenthe two parallel plates of the capacitor will be shorted by the water incontinuous phase. Unfortunately, this phenomena exists even though oilmay still comprise a high percentage (e.g., some 40 or 50% or more) ofthe overall mixture.

Of the prior known devices, U.S. Pat. No. 4,774,680 to Agar is relatedto the present invention. The Agar patent addresses the problem ofsingle curve characteristics. Agar solves the prior problem ofdetermining a fundamental measurement based upon an electrical propertyof the fluid. Corrections to the fundamental measurement are not taughtor suggested by the Agar patent.

A relatively typical capacitance probe for use in determining oil/waterratios is found in U.S. Pat. No. 3,200,312 to Callaghan. Callaghanrelies on the measurement of the mixture's dielectric constant. As such,the probe must be non-functional when conductive water is in thecontinuous phase.

Yet another capacitance-type probe is taught in U.S. Pat. No. 3,025,464to Bond probe is designed specifically for pipeline use where there istypically low water content and oil is in the continuous phase. For thatpurpose, the Bond probe will function adequately. However, because theBond probe is a capacitance probe, it will not function in mixtureswhere water becomes the continuous phase.

Still another prior art capacitance probe is shown in U.S. Pat. No.3,523,245 to Love et al. It has the same shortcomings as the prior artreferences mentioned above. In fact, FIG. 2 of the Love et al. patentdepicts a graph for water fraction versus probe capacitance. It is notedthat the water fraction portion of the graph does not go above 0.5. Infact, the Love et al reference in discussing FIG. 2 specifally statesthat when the water fractions get above 0.5, the water tends to separateout and the capacitance quickly approaches the value at free water.

U.S. Pat. No. 3,368,147 to Graham teaches a capacitance measuringcircuit to determine the sediment and water content of oil wellproduction. Because Graham relies on capacitance, such reference is alsoinsufficient to determine oil/water rations where water is in thecontinuous phase.

U.S. Pat. No. 3,550,019 to Thomas seems to teach a linearizing circuitfor net oil analyzers. However, Thomas does not teach the use of adigital linearizer or any means of overcoming the jump in the electricalcharacteristic of the mixture as the oil/water mixture moves from oilbeing in the continuous phase to water being in the continuous phase.

Yet another net oil computer is described in U.S. Pat. No. 3,385,108 toRosso. Rosso relies on a capacitance probe and does not teach the use ofa digital linearizer or any means of overcoming the jump in theelectrical characteristic of the mixture when the oil/water mixture goesfrom oil being in the continuous phase to water being in the continuousphase.

Another typical capacitance probe having the same inadequacies as thoseprobes mentioned above is found in U.S. Pat. No. 3,006,189 to Warren etal.

A few techniques are available to measure the electrical properties ofthe mixture. For example, the conductivity of the mixture may bemeasured at a high frequency. While such techniques avoid the saturationeffect which is typical of measuring capacitance, they produce twodistinct, non-linear curves or families of curves of output signal. Withthe two distinct non-linear curves, the conductivity curves, the currentmay be plotted against the percentage of water in the mixture. Theconductivity curves may be empirically or theoretically derived. Thefirst set of these curves is for the case where the water is in thecontinuous phase, while the second set of these curves is for the casewhere oil is in the continuous phase. It should be understood that the"step jump" between these curves does not occur at a predeterminedoil/water ratio. With respect to the "step jump" between the curves,other variables are involved including (as examples) the surface tensionof the fluids and the amount of emulsifying chemicals present.

It is therefore a feature of the present invention to provide anapparatus and method for determining the percentage of water present ina mixture where either oil or water is in the continuous phase.

Yet another feature of the present invention is to provide an apparatusand method for determining the percentage of water in an oil/watermixture where the amount of water present is in the range from 0 to 100percent.

Still a further feature of the present invention is to provide a methodand apparatus for determining the water content in oil/water mixtures bymeasurement of the mixture's electrical properties wherein the outputsignal is linearized.

Still another feature of the present invention is to teach a method andapparatus for determining whether oil or water is in the continuousphase by measuring an electrical property of the mixture.

Yet a further feature of the present invention is to provide a methodand apparatus for selecting one of two curves which represent thepossible conditions of the media.

It is a further feature of the present invention to provide an apparatusand method for determining the percentages of oil and water in anoil/water mixture by measuring its electrical properties wherein it isdetermined whether the oil or the water is in the continuous phase.

Yet another feature of the present invention is to provide twoempirically or theoretically derived curves which plot percentage ofwater versus current which allows determination of whether the oil orthe water is in the continuous phase.

Briefly state, the foregoing and numerous other features, object andadvantages of the present invention will become readily apparent uponreading the detailed description, claims and drawings set forthhereinafter. These features, objects and advantages are accomplished byutilizing a microprocessor or comparator circuit which is able todistinguish between oil being in the continuous phase and water being inthe continuous phase based on the electrical properties of the mixture.For example, the conductivity of the media may be measured at a highfrequency. While these techniques avoid the saturation effect which istypical of measuring capacitance, they produce two distinct, non-linearcurves of output signal typically plotting current versus the percentageof water in the mixture. These curves may be empirically ortheoretically derived. The first of these curves is for the case wherethe water is in the continuous phase, while the second curve occurswhere oil is the continuous phase. It should be understood that thechange in phase does not occur at a predetermined oil/water ration.Other variables are involved including droplet size, surface tension andemulsifying chemicals present. Typically however, the change occurs whenthe amount of water present in the mixture is in the range ofapproximately 35 to 75 percent of the total. Thus, just measuring theproperties of the mixture does not give the complete solution. Becausethere are two distinct families of curves or equations it is necessaryto determine which curve or equation is to be used in calculating thepercentage of water present.

SUMMARY OF THE INVENTION

To achieve the foregoing objects, features, and advantages and inaccordance with the purpose of the invention as embodied and broadlydescribed herein, an apparatus and method for determining the percentageof a fluid in a mixture of fluids is provided. Among other advancements,the present invention is guided by the discovery that one of thevariables is droplet size. The size of the droplets comprising themixture has a marked effect on the apparent conductivity of the mixtureand thus the energy absorbed. Droplet size has been found to bedetermined by the shearing velocity, i.e., the viscosity and the surfacetension of the mixture. However, the most critical of the parameters isbelieved to be the velocity.

According, therefore, to the present invention, there is provided amethod of determining the percentage of a fluid present in a mixture offluids flowing through a predetermined region of a conduit. The methodcomprising obtaining a measurement of at least one electrical propertyof the mixture in the region, measuring the speed of flow of the mixturein the region, and employing the measurement and the speed of flow toapply a secondary correction to the fundamental measurement, to get anaccurate percentage of the fluid present in the mixture of fluidsirrespective of the droplet size or other characteristics of themixture.

By way of example, the speed of flow of the mixture is used in thederivation of the correct percentage, by automatically correcting forthe effects of variation in the shape and size of the particles on theelectrical property of the mixture. Preferably, the temperature of themixture in the selected region is also obtained to apply one or moresubsequent degrees of correction of the percentage of the fluid presentin the mixture. Typically, velocity is the first degree correction.

Typically, the mixture can contain a mixture of a first and a secondliquid. When an electrical property is plotted against the percentage,two data curves (or families of data curves) are obtained which curvesare separated from each other. The two data curves represent the firstliquid in the continuous phase and the second liquid in the continuousphase, respectively. The said first and second liquids may be water andoil, respectively.

The derivation of the percentage, percentage, preferably, involvesdetermining whether the first or second liquid is in the continuousphase, selecting the appropriate data curve, and obtaining a readingfrom the latter. Preferably, the determination as to whether the firstor second liquid is in the continuous phase is effected by comparing themeasurement of the electrical property or properties to a predeterminedvalue. Thereafter, one data curve or family of curves is selected whenthe measurement is above the predetermined value, and the other datacurve or family of curves is selected when the measurement is below thepredetermined value.

In the specific example of an oil/water mixture, the step jump from onefamily of curves to the other may occur when the amount of water in themixture is in the range of approximately 35 to 75 percent of the total.Thus, just measuring the electrical properties of the mixture is not thecomplete solution because for the same percentage of mixture, aplurality of distinct values of electrical properties exist. Since thereare two distinct sets of curves and respective equations to describe thecurves, it is necessary to determine which curve or equation is to beused in calculating the percentage of water present.

As indicated above, the step jump occurs in the data when the mixturechanges from oil being in the continuous phase to water being in thecontinuous phase. It is imperative to eliminate the step jump from thedata and to linearize the two distinct curves or families of curves.

The step jump represents a rapid change in the conductivity of themixture. This change in conductivity may be measured by a conductivitymeter or energy absorption detector, typically for example, in the unitsof milliamps of output. Information concerning the change inconductivity may be used by a comparator to select one of two memorieswhich are respectively programmed with data relating to water being inthe continuous phase and to oil being in the continuous phase. By way ofexample, it has been determined that an oil/water monitor in aparticular configuration measures a current of approximately less than 5milliamps, when oil is in the continuous phase. Alternately, it has beendetermined that an oil/water monitor in a particular configurationmeasures a current of greater than approximately 5 milliamps, when wateris in the continuous phase. The linearized output from the selectedmemory may be fed to an output stage, display or multiplier. Themultiplier may be used to determine the net water content of the mixtureby multiplying the gross flow rate by the percentage of water present.The difference between the gross flow rate and the net water contentequals the net oil present.

In the above example, the characteristics of oil/water mixtures havebeen used as an example. There are however other physical examples of adistinct "jump" from one family of curves to another, i.e., adiscontinuity in the function describing the physical phenomena. Anexample of such a discontinuous phenomena is the change from laminarflow to turbulent flow. The "jump" occurs in passing from laminar flowto turbulent flow at a Reynolds number of approximately 2000. Thecorrections practiced by the present invention can be applied to anysuch discontinuous functions.

According, therefore, to another aspect of the present invention, thereis provided an apparatus for determining the percentage of a fluidpresent in a mixture of fluids flowing through a predetermined region ofa conduit. The apparatus comprising electrical property or properties ofthe mixture in the region; flow measuring means for measuring the speedflow of the mixture in the region; and calculator means arranged toreceive signals from the flow measuring means to apply a correction tothe signal from the electrical property measuring means to calculate thecorrect percentage therefrom.

The apparatus preferably comprises temperature measuring means formeasuring the temperature of the mixture in the region, the calculatormeans being arranged to receive signals from all said measuring meansand to calculate the percentage therefrom. The calculator means maycomprise memory means programmed with data relating to whether a firstliquid or a second liquid of the mixture is in the continuous phase, thecalculator means having data selection means arranged to select the datato be employed in calculating the percentage. The data selection meansmay comprise a comparator arranged to select the data to be employed incalculating the said percentage, the comparator comparing the saidmeasurement with a predetermined value and selecting the data inaccordance with whether the said measurement is above or below thepredetermined value. The flow measuring means may be arranged to send asignal representative of flow through a conduit to a multiplier wherethe flow is multiplied by the percentage to produce an indication of thenet flow of the fluid whose percentage has been calculated. A subtractormay be provided for subtracting the last-mentioned net flow from thegross flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings which are incorporated in and constitute apart of the specification, illustrate a preferred embodiment of theinvention and together with the general description of the inventiongiven above and the detailed description of the preferred embodimentgiven below, serve to explain the principles of the invention. Theinvention is illustrated, merely by way of example, in the accompanyingdrawings, in which:

FIG. 1 and 2 are illustrations of possible effects on the conductivityof an oil/water mixture, respectively, of large and small droplets;

FIG. 3 is an elevation cross-sectional view of a preferred embodiment ofan oil/water monitor which may be used in an apparatus practicing to thepresent invention;

FIG. 4 is a schematic diagram of an embodiment of an apparatus accordingto the present invention;

FIG. 5 is a graph of two empirically derived sets of curves in whichcurrent absorbed or admittance is plotted against the percentage ofwater in an oil/water mixture, and

FIG. 6 is a schematic view of a circuit which may be used in anoil/water monitor forming part of an apparatus according to the presentinvention.

The above general description and the following detailed description aremerely illustrative of the generic invention, and additional modes,advantages, and particulars of this invention will be readily suggestedto those skilled in the art without departing from the spirit and scopeof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention as described in the accompanying drawings.

The present invention is, in part, based on the discovery that themeasurement of the conductivity or other electrical property of amixture of fluids, such as an oil/water mixture, flowing through apredetermined region of a conduit is affected by the size and shape ofthe droplets of at least one of the liquids of the mixture, e.g., oilbeing in a continuous phase of another liquid of the mixture, e.g.,water. This phenomena is illustrated in FIGS. 1 and 2.

In FIG. 1, there is shown diagrammatically a conductivity meter 1 havingspaced apart positive and negative electrodes 2 and 3, respectively. Anoil/water mixture 4 comprising 30% oil and 70% water flows through thespace between the electrodes 2, 3. The mixture 4 is shown as havingwater in the continuous phase surrounding a plurality large oil droplets5. The lines of force 6 between the electrodes 2, 3 are illustrated inFIGS. 1 and 2. As will be seen, a high proportion of the lines of force6 are interrupted by the large oil droplets 5, so that the conductivityreading produced by the conductivity meter 1 will be below the truevalue.

FIG. 2 is a view similar to FIG. 1, indicating the passage through themeter 1 with an oil/water mixture 4 comprising 30% oil and 70% water. Inthe FIG. 2 case, however, the mixture 4 contains a plurality of tiny oildroplets 7. As a result of the tiny oil droplets 7, the lines of force 6are hardly affected and consequently the reading produced by theconductivity meter 1 will be above the true value.

Thus, although it is not obvious at first sight that the apparentconductivity of an oil/water mixture, which is flowing through a conduitand which has water in the continuous phase, is dependent upon the size,shape and distribution of the oil droplets, this is certainly the case.It has been found, indeed, that the apparent conductivity, and thus theenergy absorbed by the fluid, is inversely proportional to the dropletsize. Droplet size, as determined by the shearing velocity, is the mostimportant of these factors.

Accordingly, the current (I) that is measured by the conductivity meter1 as passing through the oil/water mixture 4 is a function (f) of thepercentage of water (W) in the mixture 4 and the shearing velocity orvelocity of flow (v) which is itself functionally related to theparticle size.

Thus,

    I=f(W; v).                                                 (1)

Consequently, by measuring both the velocity of flow v and the currentI, a set of simultaneous equations can be produced which can be solvedto find the percentage of water W. The parameters of the calculationscan be found empirically or by calculation.

A third parameter may also be needed if the temperature (T) of themeasured mixture varies widely. Equation (1) then needs to be rewrittenas

    I=f(W; v; T).                                              (2)

In order to solve equation (2), the temperature of the mixture 4 must bemeasured and three simultaneous equations must be solved.

Turning now to FIG. 3, there is shown therein a probe 10 mounted withina conduit 12. The conduit 12 has an inlet 11 through which an oil/watermixture passes into the conduit 12, the oil/water mixture passing out ofthe conduit 12 through an outlet end 13 of the latter. Energy istransmitted into the oil/water mixture in the conduit 12 from anoil/water monitor 14 and through the probe 10. In such manner, anoil/water monitor 14 can measure the electrical properties of themixture flowing through conduit 12. This could, for example, beperformed by measuring the conductivity, energy absorption capacitance,admittance and/or impedance of the oil/water mixture by means of theoil/water monitor 14. As used herein the term "electrical properties"includes all of such terms singly or in combination.

One such oil/water monitor 14, which can be used with the presentinvention, is the Agar Corporation OW-101 water in oil monitor asdescribed in U.S. Pat. No. 4,503,383 to Agar et al. The Agar OW-101measures the energy absorption properties of the oil/water mixture,rather than just the capacitance thereof. It is programmed with anempirically generated curve in which current in milliamps is plottedagainst the percentage of water. The curve contains a pronounced stepjump as the mixture goes from oil being in the continuous phase to waterbeing in the continuous phase. Because the location of the step isaffected by a number of variables, it can be difficult to determineprecisely what percentage of water is present. Another device which maybe used for oil/water monitor 14 is the Invalco Model No. CX-745-200GP.

Still another device can be used as oil/water monitor 14 is shownschematically in FIG. 6. It includes an alternating current generator15, a capacitor 17 and an ammeter 19. The capacitor 17 should be in theform of a probe which can be inserted into the oil/water mixture. Theammeter 19 measures current (I) so that when the water is in thecontinuous phase, the circuit can be defined by the equation:

    I=V/R

which is Ohm's Law, where I is the current through the ammeter 19, V isthe voltage of the generator 15, and R is the effective resistance ofthe oil/water mixture.

When oil is in the continuous phase, the circuit can be defined by theequation:

    I=Vjωc

where "j" is the square root of -1 , "ω" represents the radial frequencyand "c" represents the capacitance of the probe with the mixture insideit. Thus, there can be theoretically derived two distinct curves orequations representing some electrical property plotted against thepercentage of water present.

It is known that the effective capacitance of a parallel plate capacitoris given by the equation:

    C=KEA/D

where "C" is the effective capacitance, "K" is a dimensional constant,"E" is the dielectric of a medium such as an oil/water mixture betweenthe plates of the capacitor, "A" is the area of the plates and "D" isthe distance between the plates. It is further known that the effectiveresistance of a medium contained between the two plates of the capacitoris given by the equation:

    R=D/AG

where "R" is the effective resistance, "D" is the distance between theplates "A" is the area of the plates and "G" is the conductivity of themedium. Because both the dielectric constant and the conductivity of themedium are proportional to the percentage of water present in themedium, the derivation of two distinct equations is possible. However,the dielectric constant and conductivity of the medium depend not onlyon the percentages of water and oil present, but also on whichconstituent is in the continuous phase. As previously discussed, theconstituent which is in the continuous phase is affected by a number ofother variables. Therefore, in practice, it is typically simpler to usethe empirically generated curves shown in FIG. 5.

The current or electrical signal generated in the oil/water monitor 14is transmitted to a zero-&-span adjuster 16 (FIG. 4) which allows theapparatus to be calibrated. From the zero-&-span adjuster 16 the data istransmitted to an analog to digital converter and calculator 18 and to acomparator 20. The comparator 20 uses this information to select one ortwo memories, namely either a continuous water phase memory 22 or acontinuous oil phase memory 24. The calculator 18 also receives avelocity signal "v" from a digitizer 21 which digitizes an analog signalreceived from a flow meter 32 in the conduit 12. Additionally, thedigitizer 21, and consequently the calculator 18, may receive atemperature signal from a temperature measuring device 29 disposed inthe conduit 12.

The continuous water phase memory 22 and the continuous oil phase memory24 are programmed with families of curves 23 and 25, respectively, asshown in FIG. 5. As previously discussed, these curves can be arrived atempirically or theoretically. Curves 23 and 25 illustrate electricalsignal plotted against the percentage of water present in the mixture atdifferent flow velocities. The electrical signal may be in the form of ameasurement of current, voltage, frequency, energy, conductivity,capacitance, admittance, impedance or the like. It should be recognizedthat the families of curves 23 and 25 represent two separate anddistinct equation. It will be noted that the curves 23 and 25 have beenprojected, as shown by dotted lines, past the points where theyintersect a step jump 27.

The comparator 20 will normally be a microprocessor or other computingdevice which compares the measured electrical signal shown in FIG. 5 asa current with a predetermined value, for example approximately 5milliamps. If the measured current is greater than the predeterminedvalue, then water is in the continuous phase and the comparator 20selects the right hand set of curves 23. If the measured current is lessthan the predetermined value, then the oil is in the continuous phaseand the comparator 20 selects the left hand set of curves 25.

The data transmitted from the oil/water monitor 14 provides thecomparator 20 with the amount of current measured so that the comparator20 can compare the measured value to the predetermined value. Dependingon which continuous memory 22 or 24 is selected, the data is transmittedfrom the calculator 18 to that particular phase memory 22 or 24 wherethe amount of current is used to determine the percentage of waterpresent by the way of the respective curve 23 or curve 25. The digitizeddata representing the percentage of water present is then transmitted toa multiplier 26 and, simultaneously, to a digital-to-analog converter28. The data from the digital-to-analog converter 28 is then transmittedto a meter 30 where the percent of water can be directly read.

The flow rate of the oil/water mixture flowing through the conduit 12 ismeasured by the flow meter 32. The flow meter 32 is preferably apositive displacement type flow meter or some other high accuracy typeflow meter. A signal from the flow meter 32 is transmittedsimultaneously via a scaler 33 to the multiplier 26, a subtractor 34 anda gross flow totalizer 36. The gross flow totalizer 36 keeps a runningtabulation of the total volume pumped through the conduit 12. The grossflow data transmitted from the flow meter 32 to the multipler 26 ismultipled by the percentage of water data transmitted to the multiplier26 from the memories 22 and 24. The data is then transmitted from themultiplier 26 simultaneously to a net water totalizer 38 and to thesubtractor 34. The net water totalizer 38 keeps a running tabulation ofthe total amount of water which has been pumped through the conduit 12.Within the subtractor 34, the total water volume is substracted from thegross flow, the result being transmitted to the net oil totalizer 40.The net oil totalizer 40 keeps a running tabulation of the total volumeof oil which has been pumped through the conduit 12.

The graph illustrated in FIG. 5 depicts a somewhat typical step jump 27between the two non-linear sets of curves 23 and 25 which are generatedwhen oil/water ratios are determined by measuring the electricalproperties of the mixture. It is highly desirable to eliminate the stepjump 27 from the data. It is also highly desirably to linearise thedata. This is accomplished through the use of the comparator 20, thememories 22 and 24, and the calculator 18. Further, by relying on otherelectrical properties of the oil/water mixture such as energyabsorption, rather than the dielectric constant alone, a measurement maybe made of the ratio of oil to water regardless of which component is inthe continuous phase up to and including the situation where there is notrue mixture and 100 percent of the volume is water.

For purposes of clarification, the component in the continuous phase canbe defined as that liquid which contains and surrounds the droplets ofthe second liquid such that the second liquid is present within thefirst liquid in the form of individual, discrete units.

What is claimed is:
 1. A comparator circuit for use in determining phaseconditions of fluids where there is a pronounced step jump ordiscontinuity joining two independent families of curves such as in theelectrical properties of an oil/water mixture or the flowcharacteristics of a fluid, said comparator circuit receiving data froma plurality of probes such as an oil/water monitor or a turbine flowmeter comprising:(a) a first memory for storing a first data curverepresenting a first set of phase characteristics; (b) a second memoryfor storing a second data curve representing a second set of phasecharacteristics; (c) a computer means for receiving the data from theprobe, said computer means comparing the data received to apredetermined value thereby allowing said computer means to select saidfirst memory if the data received from one probe is less than thepredetermined value or to select said second memory if the data receivedfrom the probe is greater than the predetermined value, and (d) acomputer means to affect a secondary correction to the first probemeasurement.